Mechanical refrigeration systems, and related heat transfer devices such as heat pumps and air conditioners, using refrigerant liquids are well known in the art for industrial, commercial and domestic uses. In appliances and systems designed to contain items at a temperature either below or above the ambient temperature for an extended period of time, there are two important features that contribute to both the energy efficiency of such systems and to the environmental impact of such systems. The first feature or aspect of such systems is the material used as the heat transfer fluid in such systems. The second feature is the blowing agent that is used to form and/or is contained in the thermal insulation material used to help minimize the unwanted transfer of heat to or from the compartment or region being heated.